Much of the world's hydrocarbon resources are located in subterranean formations below bodies of water. By their very nature, well drilling and other well operations conducted from a platform located in a body of water present specialized dangerous conditions not present in drilling and other well operations conducted on land. In particular, severe weather conditions such as severe storms and hurricanes present an extreme danger to the continued conduct of well operations at sea.
Under severe weather conditions, it is typical to temporarily abandon well operations by disconnecting drill pipe or well tubing from the well bore and shutting in the well until the weather danger subsides at which time the well can be reentered and operations may continue. In this regard, drilling operations can be temporarily suspended leaving drill pipe in the hole through the use of a specially designed packer and valve assembly for temporary abandonment.
In order to temporarily abandon and shut in a well, a portion of the drill pipe in the hole is withdrawn and the packer and valve assembly are attached to a section of the drill pipe and lowered into the well to pack off the well and upper section of casing, typically at a depth of 100' to 300' below the wellhead. Once the packer is set, the associated valve assembly is activated by removing a subassembly of the valve which effects the closing of the valve and the disconnection of the subassembly and drill pipe above the packer so that it can be withdrawn from the well during periods of severe weather danger. The packer and valve assembly remains in the well with the drill pipe below the packer remaining attached to the packer and valve assembly thereby avoiding the lengthy process of removing multiple joints of pipe. Once the packer and valve assembly is in place and the valve-actuating subassembly is removed and withdrawn from the well, the blowout preventers at the wellhead can be activated to provide additional safety and blowout protection during the period of temporary abandonment.
A difficulty presents itself in this scheme in that all of the threaded interconnection of drill pipe, packer assembly, valve assembly and valve-actuating subassembly comprise threaded connectors requiring generally right hand torque in the make-up of the overall assembly. Furthermore, the setting of the packer typically requires the application of right hand torque while decreasing the weight of the drill string below the packer holding right hand torque. In highly deviated or horizontal wells where there is a large component of friction against the drill string, extremely high amounts of right hand torque are often necessary to set the packer. This right hand torque is also transferred through each of the threaded interconnections between the drill pipe, the packer assembly, the valve assembly and the valve-actuating subassembly. With this overtorquing of all of these threaded connections, it is impossible to predict which of the connections will "break" when opposite, left hand torque is applied preferably for the purpose of removing the valve-actuating subassembly from the valve assembly. Instead of effecting the desired rotational disconnection of the valve-actuating subassembly, the disconnection of the threaded interconnection between the packer assembly and the valve assembly often occurs thereby causing the failure of the temporary abandonment system to close off the well as desired.